Five hot, rockin’ geothermal companies

Like the natural gas sector, which has experienced an incredible boom due to new drilling techniques that allow companies to cost-effectively access unconventional gas, the geothermal sector is going through a renaissance that may open up a vast new set of resources.

Traditional utility-scale geothermal, often called hydrothermal, utilizes hot water or direct steam beneath the earth to run a turbine and generate electricity. While there’s only about 11 GW of capacity built around the world (the PV industry built 17 GW in 2010 alone), the actual electricity generation from these baseload plants typically doubles the output from an equivalent wind or solar project.

The U.S. Geological survey estimates that there are about 35 GW of hydrothermal resources left to harness in America with the potential to provide around 3% of the nation’s electricity. Last year, two researchers published a paper in the Journal of Energy Policy suggesting that the world could get about 4 percent of its electricity from traditional geothermal by 2030.

However, unconventional methods of procuring geothermal energy are not easy. In fact, they’re not really new – some of these techniques were researched in the 70’s, but were abandoned when the U.S. shifted its focus away from renewables. But now that we have better technologies and more pressing environmental and economic factors, there’s a growing list of companies working to address technology barriers. Here’s five:

Unlike traditional hydrothermal where a developer must zero in on good pockets of hot water, EGS projects can theoretically be developed almost anywhere. Developers engineer their own wells (hence, the name Engineered Geothermal Systems) by drilling deep bore holes, pumping cold water through the bedrock and letting it heat up as it moves through the natural fractures.

But drilling bore holes thousands of feet beneath the earth is expensive and time consuming; a traditional diamond-tipped drill bit needs to be replaced every hundred feet or so. Constantly taking the drill in and out of the ground increases the chance that a bore hole will collapse.

California-based Potter Drilling is working on a drilling technique called Hydrothermal Spallation that uses superheated water to bore holes – eliminating the need to use a drill bit. The company raised $4 million from Google and received $5 million in stimulus funds to develop the drill.

One of the concerns about EGS is that deep drilling and fracturing will cause seismic activity. A Connecticut-based company, GTherm, says it has an EGS solution that takes away the need to fracture the rock entirely.

GTherm has developed a closed-loop heat exchanger it calls a “heat nest” that will be deployed at the bottom of a well thousands of feet down. Rather than pump water directly in and out of the ground, it uses a heat transfer fluid that can be used to run a binary-cycle turbine designed for low-heat applications.

Don’t assume this is an easy answer to EGS though: GTherm is still in the modeling phase and will be working with the Electric Power Research Institute to deploy a 1-MW demonstration project in 2012. While an intriguing way to harness deep heat, this concept remains to be proven.

Rather than use water as a working fluid, Utah-based GreenFire Energy is using CO2 – a great way to save water in arid regions while also recycling and sequestering carbon. The process is very similar to a traditional hydrothermal power plant; however, the working fluid is pressurized, supercritical CO2 that may actually have higher heat recovery rates and lower pumping costs than water.

At first, Greenfire is focusing on naturally-occurring CO2 for its demonstration project in Arizona. But it hopes to site plants near coal facilities and utilize waste CO2 for geothermal power production. If it can prove the concept works at its 2-MW facility in the early phases of development, this could expand the number of sites suitable for geothermal projects. But again, like GTherm, we still haven’t seen if the concept works in practice.

Geothermal co-production and geo-pressured resources also have the potential to expand production while piggybacking off existing fossil fuel infrastructure. In co-production, a developer takes warm waste water from an oil and gas well and uses it to boil a working fluid and power a generator. The Texas-based company Universal GeoPower is trying to deploy this concept along the Gulf Coast where there are more than 37,000 wells that bring up billions of gallons of warm waste water each year.

Universal GeoPower will lease a well or partner with an existing pump operator, deploy 1-MW of “off the shelf” low-temperature units and sell the electricity to the local utility. Depending on water-flow rates, these projects could be used to offset on-site energy use or even be net-positive energy producers.

Like co-production, geo-pressured resources are produced in partnership with gas drillers. In this case, the hot brine is trapped and pressurized under a layer of sediment. But these fluids often contain large amounts of dissolved natural gas, which makes it economically difficult for a pure-play geothermal developer to exploit or for a natural gas driller to access. By developing projects with a hybrid approach, the brine and the methane can be separated; the brine would be used to heat a working fluid and power a low-temperature generation unit and the methane would be used in a gas turbine.

In partnership with the leading geothermal consultancy GeothermEx, Lousiana State University and the Shaw Group, Louisiana Geothermal is working on building a 5 MW project at the Sweet Lake Oil and Gas Field in Cameron Parish, Louisiana. The companies hope to be the first to prove that these two resources can be used together in an economic way.

Given that it takes so long to build a geothermal project (we’re talking many years, versus months for a solar project), it may be a while before we see these new technologies come to fruition – if at all. In the meantime, traditional hydrothermal projects will continue to dominate the geothermal market for the foreseeable future.

But there is a lot of innovation happening in this sector. With new approaches to harnessing the earth’s abundant heat, it’s not unrealistic to think that geothermal can move well beyond the conservative prediction of 4% global electricity production in the coming decades.

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11 Responses to Geothermal energy is a core climate solution

Don’t forget about geothermal heat pumps. These are conventional domestic heat pumps that obtain heat from ground water in winter, and dump AC heat into ground water in summer.These systems are much more efficient than air to air systems that use air as the source/receptor. The cost penalty is the cost of drilling the exchange well, but the greatly increased efficiency can recoup that cost in several years.

Thank you for this article. One of the most frustrating aspects about debating transitioning to renewable energy is that nearly everyone overlooks geothermal. Instead those that argue against renewables automatically assume that “renewable” means just wind and solar. I think that maybe it’s a kind of psychological block that prevents them from seeing it.

BTW… A study of Hot Dry Rock geothermal shows that has the potential in the USA to generate about 2,000 times the entire 2005 annual energy demand for the entire country.

“Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable (naturally replenished). In 2008, about 19% of global final energy consumption came from renewables, with 13% coming from traditional biomass, which is mainly used for heating, and 3.2% from hydroelectricity.[1] New renewables (small hydro, modern biomass, wind, solar, geothermal, and biofuels) accounted for another 2.7% and are growing very rapidly.[1] The share of renewables in electricity generation is around 18%, with 15% of global electricity coming from hydroelectricity and 3% from new renewables.[1][2]”

A large area in eastern West Virginia has been found to have elevated heat flow and upper crustal temperatures compared to the rest of the eastern United States. The high heat flow has been recognized based on interpretation of bottom-hole temperature (BHT) data from oil and gas drilling in the area. The high heat flow is located within the western part of the Appalachian Mountains. There are several possible explanations for the observed thermal regime given the existing data that can only be resolved by more accurate determination of the temperature and heat flow in this area. The temperatures are high enough to make this the most attractive area for Geothermal Energy development in the eastern 1/3 of the country and the heat in place is sufficient to support large scale development of Enhanced Geothermal Systems.

6. Conclusions

This reconnaissance investigation of the thermal regime of the eastern U.S. has defined a significant thermal anomaly along the Appalachian Mountain trend in West Virginia and demonstrated that temperatures high enough for electrical power generation occur at depths greater than 4 to 5 km in large areas of eastern West Virginia. This finding opens the possibility of geothermal energy production near the heavily populated Eastern Seaboard. Further research is needed to refine estimates of the magnitude and distribution of West Virginia’s geothermal resource and to understand the cause of the high heat flow values. The presence of a large, baseload, carbon neutral, and sustainable energy resource in West Virginia could make an important contribution to enhancing the U.S. energy security and for decreasing CO2 emissions.”

In my book I’d call it more a matter of improving energy efficiency, like adding insulation to a water tank to improve it’s heat retention. After all it’s still recovering energy that would otherwise be wasted from power that was already generated, but that’s a minor and debatable difference, it’s still an improvement so I’m all for it.

Here in Sonoma and Lake Counties in California we have The Geysers, for example, which already produces some naturally occuring geothermal power. It’s actually one of the biggest geothermal fields around, I think.

The limiting factor at the Geysers is I think water supply, and plans exist to pump waste water from Santa Rosa into the formation, and boost power production.

But associated with the Geysers is a huge underground pluton of hot dry rock, extending for tens of miles around the site. Even though this is I think the biggest geothermal power plant in the U.S., this geothermal site is not unusual in the western U.S. in terms of heat flow: huge areas of the Western U.S. have equivalent heat flows:

The idea of using supercritical CO2 as a working fluid is really fascinating. I know supercritical CO2 is used in oil and grease extraction from soils in environmental chemistry labs, and it is very penetrating, and permeates through the sample- possibly because there is no surface tension in a supercritical fluid. Supercritical fluids can also be tuned to become more like liguids or more like gases, by varying the pressure. If supercritical CO2 could penetrate through the rock without extensive drilling or fracking of the rock formation, that could be a huge advantage. If a basalt formation was used, we might get some simultaneous in situ mineral carbonation. If a biogenic source of CO2 was used, such as an ethanol plant, this could be carbon negative.